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- The Korean Astronomical Society (The Korean Astronomical Society)
- 계간 (Quarterly)
- ISSN : 1225-4614 (ISSN : 1225-4614)
1225-4614
- DB구축현황 : 1,227건 (DB Construction : 1,227 Articles)
총 게시글 1,227건
페이지 79/123
781
- MOON YONG-JAE
- Journal of the Korean astronomical society = 천문학회지
- 32, n.2
- pp.127-136
- 1999
- 원문 바로보기
In this study we present the study of solar active regions based on BOAO vector magnetograms and H<TEX>$\alpha$</TEX> filtergrams. With the new calibration method we analyzed BOAO vector magnetograms taken from the SOFT observational system to compare with those of other observing systems. In this study it has been demonstrated that (1) our longitudinal magnetogram matches very well the corresponding Mitaka's magnetogram to the extent that the maximum correlation yields r=0.962 between our re-scaled longitudinal magnetogram and the Mitaka's magnetogram; (2) according to a comparison of our magnetograms of AR 8422 with those taken at Mitaka solar observatory their longitudinal fields are very similar to each other while transverse fields are a little different possibly due to large noise level; (3) main features seen by our longitudinal magnetograms of AR 8422 and AR 8419 and the corresponding Kitt Peak magnetograms are very similar to each other; (4) time series of our vector magnetograms and H-alpha observations of AR 8419 during its flaring (M3.1/1B) activity show that the filament eruption followed the sheared inversion line of the quadrupolar configuration of sunspots, indicating that the flare should be associated with the quadrupolar field configuration and its interaction with new filament eruption. Finally, it may be concluded that the Solar Flare Telescope at BOAO works normally and it is ready to do numerous observational and theoretical works associated with solar activities such as flares.
782
- KIM YOUNG KWANG
- Journal of the Korean astronomical society = 천문학회지
- 32, n.1
- pp.17-39
- 1999
- 원문 바로보기
We investigate dynamical evolution of globular clusters with multi-mass component under the Galactic tidal field. We compare the results with our previous work which considered the cases of single-mass component m the globular clusters. We find the followings: 1) The general evolutions are similar to the cases of single-mass component. 2) There is no evidence for dependence on the orbital phase of the cluster as in the case of single-mass component. 3) The escape rate in multi-mass models is larger than that in the single-mass models. 4) The mass-function depends on radius more sensitively in anisotropic models than in isotropic models.
783
- LEE JEONG-EUN
- Journal of the Korean astronomical society = 천문학회지
- 32, n.1
- pp.41-53
- 1999
- 원문 바로보기
We have carried out high-resolution observations along one-dimensional cuts through the three Galactic super-shells GS 064-01-97, GS 090-28-17, and GS 174+02-64 in the HI 21 cm and CO J=l-0 lines. By comparing the HI data with IRAS data, we have derived the distributions of the <TEX>$I_{100}$</TEX> and <TEX>$T_{100}$</TEX> excesses, which are, respectively, the 100 <TEX>${\mu}m$</TEX> intensity and 100 <TEX>${\mu}m$</TEX> optical depth in excess of what would be expected from HI emission. We have found that both the <TEX>$I_{100}$</TEX> and <TEX>$T_{100}$</TEX> excesses have good correlations with the CO integrated intensity W co in all three supershells. But the <TEX>$I_{100}$</TEX> excess appears to underestimate <TEX>$H_2$</TEX> column density N(<TEX>$H_2$</TEX>) by factors of 1.5-3.8. This factor is the ratio of atomic to molecular infrared emissivities, and we show that it can be roughly determined from the HI and IRAS data. By comparing the <TEX>$T_{100}$</TEX> excess with <TEX>$W_{co}$</TEX>, we derive the conversion factor X <TEX>$\equiv$</TEX> N (<TEX>$H_2$</TEX>) /<TEX>$W_{co}{\simeq}$</TEX> 0.26 - 0.66 in the three supershells. In GS 090- 28-17, which is a very diffuse shell, our result suggests that the region with N(<TEX>$H_2$</TEX>) <TEX>$\le$</TEX> <TEX>$3 {\times} 10^{20} cm^{-2}$</TEX> does not have observable CO emission, which appears to be consistent with previous results indicating that diffuse molecular gas is not observable in CO. Our results show that the molecular gas has a 60/100 <TEX>${\mu}m$</TEX> color temperature <TEX>$T_d$</TEX> lower than the atomic gas. The low value of <TEX>$T_d$</TEX> might be due either to the low equilibrium temperature or to the lower abundance of small grains, or a combination of both.
784
- ANN HONG BAE
- Journal of the Korean astronomical society = 천문학회지
- 32, n.2
- pp.83-89
- 1999
- 원문 바로보기
We have conducted a V, I, J, and H surface photometry of a barred galaxy NGC 4314 to analyze the morphology and luminosity distribution of the galaxy. By applying a semi two-dimensional profile decomposition method, we derived the luminosity fractions and the scale lengths of the three distinct components, bulge, disk, and bar: <TEX>$L_b {\approx}0.35,\;L_d{\approx}0.35,\;L_{bar}{\approx}0.30,\;r_e{\approx}22',\;r_o {\approx} 50'$</TEX>, and a <TEX>$\approx$</TEX> 60'. The bulge of NGC 4314 seems to be triaxial due to the isophotal twists but its luminosity distribution is well approximated by the <TEX>$r^{1/4}$</TEX>-law.
785
- LEE HYUNG MOK
- Journal of the Korean astronomical society = 천문학회지
- 31, n.2
- pp.95-99
- 1998
- 원문 바로보기
We report preliminary results of an on-going survey of optically selected barred galaxies with <TEX>$^{12}CO$</TEX>(J=1-0) line. The entire sample is composed of about 100 bright barred galaxies (<TEX>$B_T{\le}13$</TEX>) with small inclination angle. Most of the galaxies are relatively nearby with receding speed less than 10,000 km/sec. In the first observing run, we have observed central parts of 18 galaxies and detected CO emissions from 5 galaxies (NGC521, 2525, 4262, 4900, and 7479). Most of these galaxies are not observed with CO previously, except for NGC7479 which has been studied at various wavelengths. The peak antenna temperature of detected galaxies ranges from about 30 to 300 mK.
786
- LEE KANG HWAN
- Journal of the Korean astronomical society = 천문학회지
- 31, n.1
- pp.19-26
- 1998
- 원문 바로보기
The wide field <TEX>$(\~20'\times20')$</TEX> CCD photometry has been performed for more than 4,000 stars over a whole region of NGC 362 which is located inside the SMC halo. The Color-Magnitude diagram (CMD) and luminosit function (LF) for red giant branch (RGB) stars are presented, discussing a distinct bump along the RGB and some blue stars appearing in the blue horizontal branch (BHB) and above BHB. The anomalous globular cluster NGC 362 with highly populated red horizontal branch (RHB) stars is compared with the another anomalous globular cluster NGC 288 with highly populated BHB stars. A metal-rich, young blue component and metal-'poor, old red component of the SMC halo stars are examined.
787
- KIM MINSUN
- Journal of the Korean astronomical society = 천문학회지
- 31, n.2
- pp.109-115
- 1998
- 원문 바로보기
We show that the low density regions of the matter distribution preserve the properties of the primordial density field better than the high density regions. We have performed a cosmological N-body simulation of large-scale structure formation in the standard CDM cosmology, and studied the evolution of statistics of under-density and over-density regions separately. The rank-order of the under-density regions is closer to the original one compared to that of the over-density regions. The under-density peaks (or voids) has moved less than over-density peaks (or dense clusters of galaxies) from their initial positions. Therefore, the under-density regions are more useful than the over-density regions in the study of the statistical property of the primordial density field.
788
- KYEONG JAE-MANN
- Journal of the Korean astronomical society = 천문학회지
- 31, n.2
- pp.127-140
- 1998
- 원문 바로보기
With a large format near-infrared camera at the 2.2-m telescope on Mauna Kea Observatory, we performed J K near-infrared observations for the metal rich globular cluster NGC6712. This cluster lies near the galactic plane and therefore suffers heavy reddening. We present the near-infrared color-magnitude diagram and also derive the metallicity ([Fe/H] <TEX>${\~}-0.96{\pm}0.27$</TEX>) as well as its distance modulus ((m - M) <TEX>${\~}13.42{\pm}0.12$</TEX>).
789
- LEE DONG WOOK
- Journal of the Korean astronomical society = 천문학회지
- 31, n.1
- pp.27-37
- 1998
- 원문 바로보기
We have made semi-analytical studies to investigate the configurations of caustics and the probability distribution of the flux factor K for the binary microlensing including external shears. A parametric equation of critical curve is derived in a 4th order complex polynomial. We present the topological dependencies of the caustics for selected gamma parameters (0, 0.3, 0.6, 1.3, 2.0, and 2.5) and convergence terms (0., 0.4, 0.8, 1.2, 1.6, and 2.0). For the purpose of analyzing the efficiency of High Amplification Event (HAE) on each caustics, we examine the probability distribution of the flux factor by a Monte Carlo method. Changing the separation of the binary system from 0.8 to 1.3 (in normalied unit), we examine the probability distribution of the K-values in various gamma parameters. The relationship between gamma parameters, seperations and their probabilties of the flux factor K have been studied. Our results show that the relatively higher K values (K>1.5) are increased as increasing the separation of the binary system. We therfore conclude that, in the N-body microlensing, the probabilities of higher HAEs are inversely proportional to the star density as well. We also point out that the present research might be used as a preliminary step toward investigating heavy N-body microlensing simulations.
790
- MINH Y. C.
- Journal of the Korean astronomical society = 천문학회지
- 31, n.2
- pp.117-125
- 1998
- 원문 바로보기
We have observed the 10-9 transitions of <TEX>$HC_3N$</TEX> and its <TEX>$^{13}C$</TEX> substitutes (<TEX>$H^{13}CCCN,\;HC^{13}CCN$</TEX>, and <TEX>$HCC^{13}CN$</TEX>), and the vibration ally excited 12-11 (<TEX>$v_r=1$</TEX>) <TEX>$HC_3N$</TEX> transition toward the Sgr B2 molecular cloud. The observed <TEX>$HC_3N$</TEX> emission shows an elongated shape around the Principal Cloud (<TEX>$\~$</TEX>4.5 pc in R.A. <TEX>$\times$</TEX> 7.4 pc in Decl.). The optically thin <TEX>$H^{13}CCCN$</TEX> line peaks around the (N) core and we derive the total column density <TEX>$N(H^{13}CCCN) = 4 {\times}10^{13} cm^{-2}$</TEX> at this position. Toward the 2' N cloud which shows the peculiar chemistry, the <TEX>$HC_3N$</TEX> lines show enhancements compared to the extended envelope. The shocks of the 2' N may have resulted in the enhancement of <TEX>$HC_3N$</TEX>. The hot component of <TEX>$HC_3N$</TEX> is strongly concentrated around the (N) core and its HPW is <TEX>$\~$</TEX>0.9 pc in diameter. We derive the lower limit of the abundance ratio <TEX>$N(HC_3N)/N(H^{13}CCCN)$</TEX> to be larger than 40 in most regions except the (M) and (N) cores. The fractionation processes of <TEX>$^{13}C $</TEX>at this region may not be as effective as previously reported.